2.

4 Linear Material Properties

The material properties used by the element type are listed under "Material Properties" in the input table for each element type. A brief description of allmaterial properties not described with the elements is given in Table 2.4-1 at the end of this section. These properties (which may be functions oftemperature) are called linear properties because typical non-thermal solutions with these properties require only a single iteration. Properties such as stress-strain data (described in Section 2.5.1) are called nonlinear properties because an analysis with these properties requires an iterative solution. Linear materialsthat are required for an element, but which are not defined, use the default values as described below (except that EX and KXX must be input with a non-zerovalue). Any additional materials are ignored. See Section 2.1 of the ASYS Theory Reference for material property details.For orthotropic materials, the X,Y, and Z part of the label (e.g. EX, EY, and EZ, or KXX, KYY, and KZZ) refers to the direction (in the element coordinatesystem) that that particular property acts in. The Y and Z directions of the properties default to the X direction (e.g., EY and EZ default to EX) to reduce theamount of input required. In addition, PRYZ and PRXZ default to PRXY; NUYZ and NUXZ default to NUXY; GXY defaults to EX/(2(1+PRXY)) and GYZand GXZ default to GXY for isotropic materials (for orthotropic materials, actual values of GXY should be input; if not input, GXY defaults toEX*EY/(EX+EY+2*PRXY*EX).Important: If properties KXX, KYY, and/or KZZ vary with temperature, this denotes a nonlinear analysis problem.Poisson's ratio may be input in either major (PRXY, PRYZ, PRXZ) or minor (NUXY, NUYZ, NUXZ) form, but not both for a particular material. The majorform is converted to the minor form during the solve operation [SOLVE]. For isotropic materials, the major and minor forms are equivalent. Solution output isin terms of the minor form, regardless of how the data was input. If no Poisson's ratio properties are input, the minor form is used by default and 0.3 is usedfor NUXY. If the major form is to be used, PRXY must be input. If a zero value is desired, input the label (NUXY or PRXY) with a zero (or blank) value.Poisson's ratio should not be equal to 0.5 for an isotropic material.Material dependent damping (DAMP) is an additional method of including structural damping for dynamic analyses and is useful when different parts of themodel have different damping values. If DAMP is included, the DAMP value is added to the BETAD value as appropriate (see Section 15.3 of the ASYSTheory Reference). Special purpose elements, such as COMBIN7, LINK11, CONTAC12, MATRIX27, FLUID29, and VISCO88, generally do not requiredamping. However, if material property DAMP is specified for these elements, the value will be used to create the damping matrix at solution time.For axisymmetric analyses, the X, Y, and Z labels refer to the radial (R), axial (Z), and hoop ( ) directions, respectively. Orthotropic properties given in theR,Z, system should be input as follows: EX=ER, EY=EZ, and EZ=E . An additional transformation is required for Poisson's ratios. If the given R,Z,properties are column-normalized (see Section 2.1 of the ASYS Theory Reference), NUXY=NURZ, NUYZ = NUZ = (ET/EZ) *NU Z, and NUXZ=NUR .If the given R,Z, properties are row-normalized, NUXY=(EZ/ER)*NURZ, NUYZ=(E /EZ)*NUZ =NU Z, and NUXZ=(E /ER)*NUR .EMIS defaults to 1.0 if not defined; however, if defined with a 0.0 (or blank) value, EMIS is taken to be 0.0.When you use the MP command to enter values for the thermal coefficient of expansion ( ), the program interprets those values as mean values, taken with2.4 Linear Material Properties (UP19980821 ) http://www.ansys.stuba.sk/html/elem_55/chapter2/ES2-4.htm#S2.41 of 5 02/07/2014 15:02respect to some common datum or definition temperature. For instance, suppose you measured thermal strains in a test laboratory, starting at 23 C, and tookreadings at 200, 400, 600, 800, and 1000. When you plot this strain-temperature data, the slopes of the secants to the strain-temperature curve would bethe mean values of the coefficient of thermal expansion, defined with respect to the common temperature of 23